This invention relates to a working method and a working apparatus, each for a workpiece being conveyed wherein a movable base is provided alongside of a conveyor conveying a workpiece such as a vehicle door or the like mounted on a carrier. The base is movable in the longitudinal direction in which the workpiece is being conveyed. A robot mounted on the movable base is used to apply predetermined working to the workpiece being conveyed by the conveyor.
An apparatus of this kind is known from the Japanese Unexamined Utility Model Registration Application Publication No. JIKKAISHO No. 61-137434 wherein a clamp means is provided on a movable base, the clamp means being movable in the longitudinal direction and operated to clamp a carrier by signals from a detecting means that detects the carrier. The clamp means having clamped the carrier is then advanced as it follows the carrier until the workpiece mounted on the carrier is moved to attain a predetermined positional relationship with respect to the movable base. Then the clamp means is fixed to the movable base and the movable base is advanced synchronously with the carrier. In this condition, a predetermined working is applied to the workpiece by the robot mounted on the movable base.
In the working apparatus arranged as above, while it is possible to obtain a predetermined positional relationship between the workpiece and the robot relative to the longitudinal direction of the conveyor, there is no guarantee that there can be obtained a predetermined positional relationship therebetween with respect to the lateral and vertical directions, so that more working errors are likely to occur due to vertical and/or lateral positional misalignments of the workpiece with respect to the robot.
In this case, if it is arranged such that the workpiece may be properly positioned vertically and laterally with respect to the carrier and supported in that position, the workpiece will then be properly positioned vertically and laterally, through the carrier, with respect to the movable base, that is, with respect to the robot mounted on the movable base, when the carrier is clamped by the clamping means.
This arrangement can eliminate occurrence of such a problem as the one just mentioned above. However, it does have a significant drawback in that a number of positioning members have to be mounted on the carrier with the result that equipment cost per carrier is much increased and in addition workability with respect to setting the workpiece onto the carrier becomes poor, thus hampering further productivity improvement.
In view of the foregoing, the object of the present invention is to provide a working method and a working apparatus, each for a workpiece being conveyed, wherein the workpiece can be accurately positioned in three orthogonal directions with respect to the robot while being conveyed even when the workpiece is not previously mounted on the carrier according to specific positioning requirements.